Novak Djokovic and Serena Williams began the defence of their Australian Open titles in contrasting fashion as the first Grand Slam of the year started with a bang on Monday, with Roger Federer showing his class again with another grand showing.

With doubts hanging over her fitness, after missing the leadup tournaments to the first Grand Slam of the year, Serena was made to work really hard by the 35th ranked Camila Giorgi in a 6-4, 7-5 victory at the Rod Laver Arena.

It was the unforced errors, particularly the double faults, which proved to be the difference between the two players in the end, with Giorgi serving up 12 of those to Serena's two. The American only had 22 unforced errors in total to Giorgi's 32, with the victory, eventually, coming in one hour and 45 minutes.

The first match at the Rod Laver Arena was much more straightforward as Petra Kvitova eased past Luksika Kumkhum 6-3, 6-1. Like Serena, Kvitova had also pulled out of the warm-up tournaments, with a stomach virus, but the Czech produced the goods when she needed to, to see off her opponent from Thailand.

"Yeah, I'm very pleased with how I played today," Kvitova was quoted as saying by the Australian Open's official website. "For me, it was my first match of the season so I was really glad I got through.

"I had a great offseason but when I got to Shenzhen I got a stomach virus or something. I didn't eat very well so I lost some weight but feeling much better now."

There was an upset in the women's draw, though, as Caroline Wozniacki, seeded 16, was dumped out in the first round by Kazakhstan's Yulia Putintseva, who won 1-6, 7-6 (7-3), 6-4.

In men's singles, Djokovic, expectedly, had little trouble dispatching South Korean youngster Hyeon Chung 6-3, 6-2, 6-4 in one hour and 55 minutes, while Federer was also smooth as ever in his 6-2, 6-1, 6-2 win over Nikoloz Basilashvili.

Kei Nishikori laid an early marker with a convincing 6-4, 6-3, 6-3 victory over Philipp Kohlschreiber. Playing the experienced German, ranked 34 in the world, Nishikori was expected to face a stiff challenge, but the Japanese showed why he should be considered an outside favourite for the title in Melbourne with an authoritative performance.

"It's great to finish in three sets, especially against Philipp," Nishikori, seeded seven in the Australian Open, said. "It was not easy but I played some great tennis. My body feels good and everything was good on the court."

India's Yuki Bhambri, making his first appearance in the singles main draw of a Grand Slam, put up a valiant effort in the first set against Tomas Berdych, but the semifinalist from last year had too much in the bag in the end, winning 7-5, 6-1, 6-2.

"It gives me such extra confidence," Berdych said after winning in one hour and 45 minutes. "There's a lot of long matches to go and I'm pleased to handle it the way I did today."